The structure-function paradigm of the diverse, sensitive, highly evolved, vertebrate olfactory pathway provides the foundation for electronic olfactory sensors. A particularly advantageous electronic olfactory sensor detects the changes in fluorescence from an indicator imbedded in a polymer produced by weak, non-specific interactions between the odor and an array of polymers. Unfortunately, instabilities caused by saturation effects and photobleaching, a result of the excessive excitation intensity necessary for an array of photodiode detectors, limit their sensitivity and overall performance. Based on recent advances in Geiger-mode micro-Avalanche Photodiode (uAPD) arrays at Radiation Monitoring Devices, Inc. (RMD) and olfactory sensors investigated at Tufts University, School of Medicine, we propose to develop a high sensitivity, low power, olfactory sensor. The fluorescence light will be detected by a uAPD array with single-photon sensitivity, enabling a substantial reduction in the incident excitation intensity. In Phase I we successfully investigated various substrates and demonstrated the feasibility of our sensor concept by constructing a simple Phase I prototype sensor. In Phase II, we will continue to research appropriate sensors, develop a prototype to meet the performance specifications determined in Phase I, and investigate the interactions between the odor, and the fluorophore imbedded polymer. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE